PNIVEBSITY  OF  CALIFOBNIA  PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


CONTROL  OF  THE  POCKET  GOPHER 

IN  CALIFORNIA 


BY 
JOSEPH  DIXON 

Contribution  from  the  Museum  of  Vertebrate  Zoology,  University  of  California 


BULLETIN  No.  340 

February,  1922 


UNIVERSITY  OF  CALIFORNIA  PRESS 

BERKELEY 

1922 


David  P.  Barrows,  President  of  the  University. 

EXPERIMENT  STATION  STAFF 

HEADS  OF  DIVISIONS 

Thomas  Forsyth  Hunt,  Dean. 

Edward  J.  Wickson,  Horticulture  (Emeritus). 

,  Director  of  Resident  Instruction. 

C.  M.  Haring,  Veterinary  Science,  Director  of  Agricultural  Experiment  Station. 

B.  H.  Crocheron,  Director  of  Agricultural  Extension. 

II.  J.  Webber,  Citriculture,  Director  of  Citrus  Experiment  Station. 
Hubert  E.  Van  Norman,  Dairy  Management. 
William  A.  Setchell,  Botany. 
Myer  E.  Jaffa,  Nutrition. 
Ralph  E.  Smith,  Plant  Pathology. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shaw,  Soil  Technology. 
John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 
Frederic  T.  Bioletti,  Viticulture  and  Fruit  Products. 
Warren  T.  Clarke,  Agricultural  Extension. 
Ernest  B.  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
James  T.  Barrett,  Plant  Pathology. 
Walter  Mulford,  Forestry. 
Fritz  W.  Woll,  Animal  Nutrition. 
W.  P.  Kelley,  Agricultural  Chemistry. 
H.  J.  Quayle,  Entomology. 
Elwood  Mead,  Rural  Institutions. 
H.  S.  Reed,  Plant  Physiology. 
L.  D.  Batchelor,  Orchard  Management. 
J.  C.  Whitten,  Pomology, 
f  Frank  Adams,  Irrigation  Investigations. 

C.  L.  Roadhouse,  Dairy  Industry. 
R.  L.  Adams,  Farm  Management. 

W.  B.  Herms,  Entomology  and  Parasitology. 

F.  L.  Griffin,  Agricultural  Education. 
John  E.  Dougherty,  Poultry  Husbandry. 

D.  R.  Hoagland,  Plant  Nutrition. 

G.  H.  Hart,  Veterinary  Science. 

L.  J.  Fletcher,  Agricultural  Engineering. 
Edwin  C.  Voorhies,  Assistant  to  the  Dean. 


t  In   cooperation  with   Office  of  Public  Roads   and   Rural   Engineering,   U.    S. 
Department  of  Agriculture. 


CONTROL  OF  THE   POCKET  GOPHER 

IN   CALIFORNIA 

By  JOSEPH  DIXON* 


The  damage  done  by  the  pocket  gopher  in  California  is  estimated 
at  eight  million  dollars  a  year.  The  depredations  by  this  rodent  are 
locally  numerous,  extend  over  nearly  the  entire  state,  and  go  on  all  the 
year.  The  losses,  taken  one  by  one,  may  be  trivial,  but  in  the  aggregate 
they  are  formidable. 

FEATURES  OF  THE  POCKET  GOPHER 

Because  most  of  the  gopher 's  work  is  done  in  the  dark,  either  under- 
ground or  at  night,  the  disastrous  results  of  the  animal's  activities  are 
better  known  to  most  people  than  is  the  animal  itself.  The  pocket 
gopher  is  a  small,  chunky,  short-legged,  burrowing  rodent,  with  large 
protruding  front  teeth,  fur-lined  cheek  pouches  or  pockets  (which 
are  used  to  carry  food,  not  dirt,  and  which  open  outside  the  mouth), 
small  ears  and  eyes,  and  a  short  tail,  often  naked  at  the  tip.  The 
gopher  averages  smaller  than  either  the  common  house  rat  or  the  wood 
or  "trade"  rat,  but  there  are  often  great  differences  in  size,  especially 
between  the  sexes. 

The  Pocket  Gopher  Compared  with  Animaj,s  Sometimes  Mistaken  for  It 


External  cheek 

Tail 

Fur 

pouches 

Front  teeth 

Gopher 

short,  2  to  3  in., 
often  naked  at  tip 

harsh 

always  present 

large, 

protruding 

Mole 

short,  1  to  1%   in. 

velvety 

none 

small 

Meadow  mouse 

short,  1  to   1%   in. 

harsh 

none 

small 

Kangaroo 

rat 

long,  6  to  10  in. 

silky 

always  present 

small 

COMPARISON  OF  MOLE  AND  POCKET  GOPHER 

The  nature  and  work  of  these  two  animals  are  frequently  confused, 
but  they  differ  greatly.  The  mole  is  not  a  rodent  (gnawer)  at  all.  It 
lives  on  animal  matter  (worms,  grubs,  and  insects),  not  on  vege- 
table matter.  A  mole  may  occasionally  be  caught  in  a  gopher  run ; 
but  the  gopher  is  the  real  cause  of  such  damage  as  eating  potatoes  and 


*  This  contribution  is  revised  from  the  original  which  constituted  Bulletin 
No.  281,  Agric.  Exper.  Sta.,  Univ.  Calif.,  published  July,  1917. 


338  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

cutting  off  roots,  which  is  sometimes  attributed  to  the  mole.  The  mole 
crowds  along  just  beneath  the  surface  in  loose  soil,  leaving  ridges  in 
which  numerous  cracks  are  visible.  The  gopher  digs  tunnels,  and  the 
sides  of  these  are  left  clean  cut.  During  dry  weather,  especially,  the 
mole  often  burrows  deeply  and  throws  up  mounds,  but  these  show  no 
trace  of  an  opening,  while  those  of  the  gopher  do.  Many  moles  have 
been  caught  for  museum  specimens  by  setting  Macabee  gopher  traps 
carefully  in  the  main  runs  of  moles  (see  p.  345,  Special  Sets). 

BBEEDING  HABITS 

The  data  recorded  with  the  2700  specimens  of  gophers,  collected 
throughout  the  state,  which  are  now  in  the  University  of  California 
Museum  of  Vertebrate  Zoology,  form  the  main  basis  for  the  following 
breeding  notes.  Gophers  have  from  three  to  twelve  young  in  a  litter. 
The  smallest  number  of  embryos  (unborn  young)  found  was  three, 
the  greatest  twelve,  while  the  average  in  twenty-eight  females  from 
many  parts  of  the  state  was  5.8.  There  is  evidence  to  indicate  that 
two  litters  in  a  season  are  frequently  raised  where  food  is  plentiful, 
as  in  alfalfa  fields. 

Out  of  eighteen  female  gophers  taken  near  San  Bernardino,  Novem- 
ber 7  and  8,  1916,  four  contained  small  embryos  and  all  but  two  of 
the  remainder  were  ready  to  breed.  The  breeding  season  can  perhaps 
best  be  gauged  by  the  period  of  growth  of  the  alfilaria,  or  "filaree," 
which,  with  malva,  among  our  native  plants,  seems  to  be  the  gopher's 
favorite  food.  The  alfilaria  is  one  of  the  earliest  plants  to  start  after 
the  first  fall  rains,  and  the  resulting  nutritious  food  supply  seems  to 
start  the  gophers  breeding.  The  nest  is  underground,  and  usually 
placed  beneath  a  stump,  rock  pile,  brush  pile,  or  similar  surface 
protection  that  will  discourage  badgers  or  coyotes  from  digging. 
The  young  remain  in  it  for  several  weeks  after  birth,  leaving 
when  they  are  nearly  one-third  grown  and  able  to  forage 
for  themselves.  In  plowing  an  abandoned  field  in  San  Diego  County 
in  the  middle  of  January,  1911,  the  writer  uncovered  at  the  bottom 
of  the  furrow  near  a  willow  stump  a  nest  containing  a  mother  gopher 
and  four  h airless,  helpless  young,  barely  able  to  crawl. 

Thn  following  dates  show  the  approximate  time  of  year  when  the 
main  crop  of  young  begin  leaving  the  nest,  though  young  may  also 
be  found  foraging  for  themselves  much  earlier  or  later  than  these  dates : 
southern  California,  March  20;  San  Joaquin  and  Sacramento  valleys, 
April  1  ;  Owens  Valley,  April  15;  foothills  of  Sierra  Nevada,  April  30; 
northwest  coast  region,  May  15. 


Bulletin   340]  CONTROL  OF   THE  POCKET   GOPHER  339 


WHEN  TO  TRAP  AND  POISON 

Obviously,  the  time  to  combat  gophers  most  successfully  is  before 
the  young  make  their  appearance  in  the  spring.  Poisoning  is  very 
effective,  but  hard  to  carry  on  in  the  dry  season,  especially  during 
August,  September,  and  October,  when  it  is  most  effective,  since  the 
supply  of  green  food  is  then  scarcest.  Trapping  and  poisoning  are 
most  easily  carried  on  soon  after  the  green  vegetation  starts  in  the 
early  winter  or  spring,  for  the  gophers  are  then  most  active.  The  wise 
old  males  which  usually  cause  the  trapper  most  trouble  seem  to  lose 
their  instinctive  caution  during  the  mating  season,  take  poisoned  bait 
readily,  and  often  blunder  blindly  into  traps  which  they  would  never 
enter  at  other  times.  Every  female  caught  at  this  time,  before  the 
young  are  born,  means  the  destruction  of  from  four  to  twelve  gophers 
for  the  current  season. 


METHODS  OF  DESTRUCTION 

The  five  most  effective  methods  of  destroying  gophers  are:  (1) 
poisoning  with  strychnine ;  (2)  trapping;  (3)  flooding;  (4)  fumigation 
with  carbon  bisulphide;  (5)  for  permanent  relief,  the  encouragement 
and  protection  of  the  gopher 's  natural  enemies,  especially  the  barn  owl 
and  the  gopher  snake. 

The  solution  of  the  gopher  problem  lies  in  a  combination  of  two 
or  more  of  the  above  methods,  rather  than  in  any  one  of  them  (see 
fig.  5).  Where  a  large  acreage  is  to  be  treated,  poisoning  with  strych- 
nine will  be  found  most  effective  in  reducing  the  pest.  Traps  are  safe, 
can  be  used  at  any  time,  and  are  effective  in  the  hands  of  a  man  who 
is  not  afraid  to  dig  and  who  uses  care  in  setting  and  in  placing  them. 
Trapping  is  especially  adapted  to  pastures,  where  there  might 
be  danger  of  poisoning  stock,  and  to  gardens,  orchards,  and  the  banks 
of  irrigation  ditches.  Carbon  bisulphide  should  be  used  only  when 
the  ground  is  wet.  Both  traps  and  carbon  bisulphide  are  good  ' '  follow- 
up"  methods  in  getting  the  gophers  which  refuse  to  take  poisoned 
bait.  Land  that  can  be  successfully  flooded,  so  as  to  drown  out  the 
gophers,  has  usually  been  graded  for  irrigated  crops  such  as  alfalfa. 
Flooding  (irrigation)  is  therefore  automatic,  and  it  is  comparatively 
easy  to  hunt  and  kill  gophers  which  are  being  flooded  out.  A  man 
that  kills  all  gopher  snakes  and  barn  owls  on  his  place  will  have  to 
fight  gophers,  and  deservedly  so. 


340  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


1.  POISONING 

The  four  things  necessary  to  poison  gophers  successfully  are:  (a) 
an  effective  poison  such  as  strychnine ;  ( b )  succulent  bait  that  will  be 
relished  by  the  gopher;  (c)  a  bait  large  enough  that  the  gopher 
must  eat  it  at  once  and  not  put  it  in  his  pocket  and  carry  it  away  to 
his  storehouse;  and  (d)  placing  of  the  bait  in  the  main  run  with  the 
least  disturbance  possible,  so  that  the  gopher  can  readily  find  it  and 
not  cast  it  out  with  the  dirt,  as  would  often  be  the  case  were  it  placed 
in  an  open  hole  or  in  a  lateral. 

In  poisoning  ground  squirrels,  it  has  been  found  that  strychnine 
is  more  readily  absorbed  through  the  membranous  cheek  pouches, 
which  open  inside  the  mouth,  than  through  the  stomach.  But 
the  fur-lined  pockets  of  the  gopher  which  open  outside  the  mouth  do 
not  readily  absorb  the  strychnine.  Hence  poisoned  bait,  such  as 
strychnine-coated  barley,  which  is  effective  on  the  ground  squirrel,  is 
not  effective  on  the  gopher.  The  gopher  often  puts  the  poisoned  grain 
in  its  pockets  and  carries  it  away  to  the  storehouse,  where  the  poison 
soon  loses  strength. 

The  cheapest  and  best  method  of  destroying  gophers,  where  a  large 
territory  is  involved,  is  by  the  use  of  vegetable  baits  poisoned  with 
strychnine.  Such  baits  are  easily  placed  in  the  main  runways  or  bur- 
rows of  the  gopher  by  aid  of  a  probe  (see  fig.  1).  The  outstanding 
advantage  of  the  probing  method  is  that  the  burrows  can  be  readily 
located  and  the  poisoned  baits  placed  in  them  with  a  minimum  dis- 
turbance. This  is  important  since  recent  field  tests  have  shown  that 
where  the  burrows  were  but  little  disturbed  the  gopher's  suspicions 
were  only  slightly  aroused  or  not  at  all.  As  a  result  of  placing  the 
bait  by  aid  of  a  probe,  40  per  cent  more  of  the  poisoned  baits  were 
taken  by  the  gophers  than  where  the  burrows  were  dug  open  and  the 
bait  placed  in  the  holes  in  the  usual  manner.  Probing  is  also  much  the 
quicker  method.  One  man,  after  becoming  familiar  with  the  use  of 
the  probe,  can  treat  several  hundred  burrows  in  a  day.  As  much  as 
five  acres  of  heavily  infested  alfalfa  have  been  gone  over  by  one  man 
in  one  day. 

The  great  disadvantage  of  the  probing  method  lies  in  the  fact  that 
in  order  to  use  the  probe  successfully  the  surface  of  the  ground  must 
be  damp  or  wet  to  the  depth  of  the  ordinary  gopher  run — six  to  eight 
inches.  The  probing  method  is  not  successful  in  dry  soils.  Tt  is  futile 
lo  probe  lor  gopher  runs  in  dry  adobe  or  any  other  soil  which  cracks 
upon  drying,  because  the  probe  drops  just  as  readily  into  a  crack  in 


Bulletin   340]  CONTROL  OF   THE  POCKET   GOPHER  341 

the  earth  as  into  a  burrow.  In  cultivated  fields  the  dry  surface  soil 
tends  to  run  in  and  to  fill  up  the  hole  made  by  the  probe. 

Gophers  are  most  likely  to  gnaw  or  girdle  orchard  trees  during 
late  summer  after  the  surface  of  the  ground  has  become  dry  and  green 
vegetation  is  scarce.  Thus  at  the  very  season  when  the  gopher  is  doing 
the  most  damage,  and  hence  his  speedy  destruction  is  most  to  be 
desired,  the  probing  method  is  of  little  use  and  the  rancher  must  then 
dig  down  to  the  main  runways  in  order  to  set  traps  or  place  poisoned 
vegetable  baits,  which  latter  are  especially  effective  at  this  time  of  year 
on  account  of  the  scarcity  of  green  vegetation. 

The  best  time  to  use  the  probe  is  just  after  the  first  good  winter 
rains  and  before  alfilaria  ("filaree")  or  other  green  vegetation  becomes 
abundant.  The  rancher  should  poison  his  land  thoroughly  at  this 
time  and  thus  kill  the  bulk  of  his  gophers  with  a  minimum  of  effort 
and  expense.  On  account  of  the  abundant  and  continuous  food 
supply,  alfalfa  fields  are  more  difficult  to  treat  effectively  than  orch- 
ards   or  open  fields. 

When  several  acres  are  to  be  poisoned  at  one  time  a  large  number 
of  baits  are  required.  These  may  be  prepared  according  to  the  follow- 
ing government  formula : 

Sweet  potatoes,  parsnips,  or  carrots  4  quarts 

Flour  paste y±  pint 

Strychnine   alkaloid,  powdered   %  ounce 

Saccharin  %2  ounce 

The  vegetables  should  be  cut  into  %-inch  cubes.  The  cubes  must  be 
large  enough  that  the  gopher  is  unable  to  pocket  them.  Failing  in 
this,  he  will  usually  begin  to  eat  the  poisoned  bait  on  the  spot.  The 
strychnine  and  saccharin  should  be  stirred  into  the  cooked  flour  paste. 
It  is  at  times  difficult  to  secure  saccharin,  and  in  that  case  a  couple 
of  tablespoonfuls  of  heavy  corn  syrup  may  be  substituted.  Gophers 
appear  to  be  less  sensitive  than  ground  squirrels  to  the  bitter  taste  of 
strychnine ;  perhaps  because  they  are  more  accustomed  to  eating  bitter 
roots.  After  the  sweetened,  poisoned  paste  has  been  prepared,  it  should 
be  poured  over  the  vegetable  cubes,  which  should  then  be  stirred  until 
each  piece  is  thinly  coated  with  it.  The  poisoned  baits  are  now  ready 
for  use  and  should  for  safety  be  kept  in  a  covered  bucket  plainly 
marked  poison. 

The  probe  (see  fig.  1)  can  readily  be  made  by  any  blacksmith  from 
a  two-foot  section  of  %-inch  round  steel.  The  metal  part  of  the  probe 
should  be  pointed  at  the  lower  end  and  bent  near  the  upper  end  to 
form  a  foot-rest  which  may  be  stepped  on  by  the  operator  and  thus 


342  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

be  of  service  in  forcing  the  probe  into  the  ground.  The  steel  point  of 
the  probe  should  be  quite  slender  to  work  well  in  hard  or  tight  ground, 
but  in  loose  sandy  soil  a  blunter  point  is  better.  The  upper  portion 
of  the  probe  is  of  wood  and  can  be  made  from  an  old  shovel  handle. 
It  should  be  reinforced  at  the  base  by  a  heavy  iron  ferrule. 


Fig.  1. — Tool  for  probing  ground  to  locate  underground  burrows  of  pocket 
gophers. 

To  locate  a  gopher  burrow  sink  the  probe  into  the  ground  10 
to  15  inches  from  a  gopher  mound,  repeating  the  operation  until  the 
burrow  is  located.  This  will  be  recognized  by  a  sudden  dropping  of 
the  probe  into  the  open  burrow.  The  opening  made  by  the  probe 
should  then  be  enlarged,  by  rotating  the  probe  or  else  by  using  the 
rounded  end  of  the  wooden  handle,  so  that  a  poisoned  cube  will  drop 
clear  into  the  open  run.  After  the  poisoned  bait  has  been  dropped 
into  the  burrow,  the  hole  made  by  the  probe  should  be  closed  by  the 
operator's  heel.  When  a  field  is  being  poisoned  the  operator  should 
kick  off  the  tops  of  all  gopher  mounds  as  he  goes  along.  If  this  is 
done,  all  mounds  made  subsequently  can  be  readily  located  and  re- 
treated, the  poison  being  placed  only  where  it  is  then  needed. 

Only  a  few  poisoned  baits  may  be  necessary  where  a  garden,  nursery 
or  lawn  is  being  damaged  by  gophers.  These  baits  may  be  prepared 
more  simply  as  follows:  Cut  carrots,  parsnips,  sugar  beets,  or  sweet 
potatoes  into  one-inch  cubes.  Then  insert  a  few  strychnine  sulphate 
crystals  into  a  slit  in  each  cube,  with  the  point  of  a  pen-knife.  Large 
raisins  may  likewise  be  slit  and  poisoned,  after  which  they  may  be 
placed  in  a  small  bottle  marked  poison  and  kept  on  hand  available  for 
use  as  need  be.  In  dry  ground,  where  the  use  of  the  probe  is  not  prac- 
ticable, the  main  runs  of  the  gopher  can  be  opened  up  in  the  same 
manner  as  when  setting  a  trap.  Then  take  a  long  slender  pointed  stick, 
so  that  the  bait  will  not  have  to  be  touched,  and  place  one  of  the 
poisoned  raisins  or  baits  a  foot  back  in  each  runway,  which  should  then 
be  tightly  closed.  The  hole  may  be  opened  up  two  days  later  and  if  the 
bait  is  gone  and  the  hole  remains  open  the  gopher  is  probably  dead. 


Bulletin  340] 


CONTROL  OF    THE  POCKET   GOPHER 


343 


Mr.  H.  A.  Hyde,  a  progressive  nurseryman  of  Watsonville,  states 
that  the  following  method  has  solved  a  serious  gopher  problem  in  his 
nursery.  Dried  prunes  are  soaked  for  1  to  2  hours  in  water  and  then 
left  to  drain.  An  incision  is  then  made  in  one  end  of  each  prune  and 
from  1  to  1%  grains  of  strychnine  inserted  into  the  slit.  A  few 
drops  of  anise  oil  are  placed  as  a  lure  on  the  other  end  of  the  prune, 
which  is  then  placed  well  back  in  a  fresh  gopher  run  in  the  usual 
manner.  The  anise  oil  is  smelled  by  the  gophers  at  some  distance 
and  appears  to  be  very  attractive  to  them.  The  use  of  anise  oil  as  a 
lure  to  rodents  in  general  is  well  known. 


Fig.  2. — a.  Best  place  to  set  traps  or  leave  poisoned  baits,  in  the  main  run 
which  is  always  kept  open  by  the  gopher,  b.  Lateral  run,  usually  partly  plugged 
with  dirt,  leading  to  the  surface  mound  c. 


2.  TEAPPING 

Almost  any  kind  of  a  trap  will  catch  gophers  sometimes,  a  few 
kinds  will  catch  them  most  of  the  time,  but  we  have  yet  to  see  the  trap 
that  will  catch  every  gopher  every  time.  Among  experienced  farmers 
throughout  the  state  there  seems  to  be  a  decided  preference  for  a 
gopher  trap  of  the  Macabee  type  (fig.  3a).  After  a  practical  test  in 
the  field,  extending  over  several  years,  the  ' '  catching  average ' '  of  this 
style  of  trap  has  been  found  to  equal  or  surpass  that  of  any  other  trap 
that  the  writer  has  been  able  to  secure.  Its  cheapness,  compactness, 
and  reliability  place  it  at  the  head  of  the  list. 

Any  form  of  explosive  trap,  or  ' '  gopher-gun, ' '  is  not  recommended 
because  of  the  degree  of  danger  which  attends  its  use. 


344  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Where  to  Set  the  Traps 

The  most  effective  "set':  for  the  Macabee  trap  is  in  the 
main  runway  (fig.  2a),  and  not  in  the  lateral  run  (fig.  25) 
that  leads  to  the  surface  mound.  This  necessitates  the  use  of  two 
traps  per  setting,  one  in  each  direction ;  but  the  results  are  so  much 
more  certain  and  quicker  that  the  catch  per  trap  per  day  is  greater 
than  where  but  one  trap  is  set  in  a  lateral  run  where  it  is  often  filled 
with  dirt  by  the  gopher.  A  common  stiff-handled  twelve-inch  iron 
spoon  is  of  great  assistance  in  finding  the  main  run  and  in  properly 
placing  the  trap.  This  spoon  had  better  be  supplemented  by  a  light 
short-handed  shovel,  for  digging  is  often  necessary  to  get  rid  of  gophers. 
The  freshest  mound  should  be  selected  and  the  probable  direction  of 
the  main  run  determined  by  noting  the  angle  of  the  dirt-plugged  hole. 
The  mounds  are  usually  situated  one  or  two  feet  distant  from,  and 
nearly  at  right  angles  to,  the  main  run. 

Method  of  procedure :  Take  the  bowl  of  the  iron  spoon  in  your 
hand  and  push  the  other  (handle)  end  of  the  spoon  into  the  ground 
where  you  think  the  lateral  is,  which  leads  from  the  mound  to  the 
main  run.  If  the  spoon  strikes  an  open  lateral  you  will  feel  it  drop 
through  the  opening.  If  the  lateral  is  filled  loosely  with  dirt  the  drop 
will  be  less  noticeable  but  still  plainly  felt.  If  it  is  plugged  tightly  it 
will  be  necessary  to  dig  down  a  little  distance  with  a  shovel  before  prob- 
ing again.  If  this  fails,  try  a  new  mound.  When  the  lateral  is  found, 
follow  it  down  to  the  main  run,  which  is  always  kept  open  by  the 
gopher.  Use  the  shovel  until  you  have  cleared  a  place  where  you 
can  set  a  trap  in  each  direction.  Smooth  out  the  hole  with  the  spoon 
but  do  not  disturb  it  more  than  is  necessary.  Set  the  treadle,  or  pan, 
so  that  a  slight  touch  will  spring  the  trap,  and  place  the  trap  well  back 
within  the  hole.  A  little  loose  dirt  should  be  left  in  the  bottom  of  the 
hole,  as  it  will  cover  the  prongs  and  front  end  of  the  trap  when  the 
trap  is  pushed  into  place.  When  in  place,  press  the  trap  down  firmly 
so  that  it  will  not  slide  back  if  the  gopher  pushes  against  it.  Then 
plug  the  burrow  with  a  clod  or  a  handful  of  grass  or  alfalfa  and  cover 
completely  so  that  no  light  can  get  to  the  trap.  A  gopher's  instinct 
prompts  him  to  close  tightly  all  open  burrows  to  keep  out  his  natural 
enemy,  the  gopher  snake  (nature's  own  gopher  trap).  Therefore,  if 
poisoned  bait  or  a  trap  be  placed  in  an  open  hole,  or  the  hole  be  left 
open,  the  poisoned  bait  will  often  be  thrown  out,  to  become  a  menace 
to  stock,  or  the  trap  sprung  by  the  dirt  which  the  gopher  pushed  ahead 
of  him  in  plugging  the  open  hole.  Set  the  traps  and  place  the  poisoned 
bail  ictll  hack  in  flic  main  runs,  which  should  then  be  tightly  closed. 


Bulletin   340]  CONTROL  OF   THE  POCKET   GOPHER  345 

The  trap  should  have  a  wire  or  light  chain  attached  to  it  and 
fastened  to  a  chunk  of  stove-wood  or,  better  still,  an  old  worn-out 
stewpan  which  will  rattle  should  you  forget  and  run  over  the  set  trap 
with  a  harrow  or  cultivator.  Coyotes  and  house-cats  dislike  the  noise, 
also,  and  do  not  drag  the  trap  far  when  they  rob  it.  In  case  only 
one  trap  is  available  when  the  main  run  is  found,  a  careful  watch  will 
often,  but  not  always,  reveal  one  or  more  little  flies  emerging  from 
the  run  where  it  is  first  opened.  These  flies  seem  to  have  a  direct  rela- 
tion to  the  gopher,  as  experiments  have  shown  that  the  side  that  they 
come  from  is  the  one  occupied  at  that  time  by  the  gopher  and  hence 
the  place  to  set  the  trap.  Traps  should  be  visited  morning  and 
evening,  or  oftener. 


Special  Sets 

Individual  gophers  will  frequently  be  found  that  refuse  to  enter 
any  sort  of  trap.  These  gophers  are  generally  old  males  and  are  likely 
to  be  the  ones  that  do  most  of  the  gnawing  on  fruit  trees.  When  one 
of  these  old-timers  repeatedly  fills  the  trap  with  dirt,  a  special  method 
becomes  necessary  to  catch  him.  Moles  also  may  be  captured  in  this 
way.  Take  a  Macabee  trap  (fig.  3a.)  and  move  the  treadle  forward 
about  an  inch  and  a  half,  placing  the  wire  which  carries  the  treadle 
below,  instead  of  above,  the  two  longitudinal  wires.  Cut  off  the  wire 
trigger  to  meet  this  change  (fig.  35) .  Then  bend  the  treadle  backwards 
at  right  angles  to  its  former  position  (fig.  4)  so  that  it  will  lie  parallel 
with  the  trap  (fig.  4c),  instead  of  sticking  up  at  right  angles  and  ob- 
structing the  runway  (as  in  fig.  45) .  Set  the  trap  so  that  it  will  spring 
easily.  Put  a  pinch  of  loose  cotton  under  the  treadle  to  keep  the  dirt 
out,  and  when  the  trap  has  been  placed  in  the  run  take  a  stick  and 
cover  the  whole  trap  with  a  thin  layer  of  loose  dirt.  Another  method 
is  to  take  a  recently  caught  female  and  rub  the  reproductive  parts  on 
the  face  of  the  treadle  of  the  regular  Macabee  trap.  A  few  drops  of 
urine  may  be  squeezed  out  during  the  process,  but  this  only  adds  to 
the  efficacy  of  the  decoy.  If  all  else  fails  catch  a  gopher  snake  and 
turn  him  loose  in  the  run. 

After  you  have  put  in  poison  or  traps,  the  tops  of  all  the  gopher 
mounds  should  be  kicked  off,  so  that  when  you  make  your  next  round 
the  newly  made  mounds  will  show  where  gophers  remain  and  where 
to  put  out  more  poison  or  traps. 


346 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 


3.  FLOODING 

As  has  been  pointed  out  above,  flooding  of  fields  is  often  an  essential 
part  of  agriculture  in  irrigated  sections.  The  main  point,  then,  is  to 
see  to  it  that  the  gophers  which  are  flooded  out  and  seek  the  higher 
borders  are  promptly  dispatched.  A  good  dog  will  do  this  effectively 
until  he  gets  tired,  and  then  the  farmer  must  be  ready  to  give  the 
gophers  proper  attention  with  the  back  of  a  shovel. 


Fig.  3. — a.  Regular  Macabee  gopher  trap, 
used  to  catch  "wise"  gophers,  and  moles. 


b.  Eeconstructed  Macabee  trap 


4.  CARBON  BISULPHIDE;  GASOLINE 
Carbon  bisulphide  is  volatile  as  well  as  inflammable  and  the  gas 
from  it  is  explosive,  so  that  caution  should  attend  its  use.  Its  use  is  ad- 
visable only  when  the  ground  is  damp  or  full  of  water,  as  the  cracks 
in  dry  ground  let  the  gas  escape.  It  does  not  seem  to  be  so  effective 
on  gophers  as  on  ground  squirrels,  for  the  gopher  burrows  are  much 
more  extensive  and  the  gopher  is  therefore  harder  to  reach.  It  is  more 
valuable  as  a  "follow  up"  method  than  for  general  application. 

There  are  two  methods  of  applying  carbon  bisulphide.  The  first  is 
to  pour  about  a  tablespoonful  on  cotton  waste,  corncobs  or  other 
absorbent  material,  which  is  then  quickly  pushed  down  the  hole  and 
the  opening  promptly  and  tightly  closed.    The  better  way  is  by  use  of 


Bulletin  340] 


CONTROL   OF    THE  POCKET   GOPHER 


347 


a  special  apparatus  which  forces  the  gas  down  the  hole.  This  is  ac- 
complished by  a  hand  bellows  attached  to  the  top  of  a  tank  that  con- 
tains the  carbon  bisulphide.  The  air  is  forced  through  a  pipe  from  the 
bellows  to  the  tank,  where  it  passes  over  the  bisulphide  and  is  carried 


O 


i> 


a 


Fig.  4. — a,  b.  Vertical  "treadle"  or  "pan"  of  regular  trap;  heavy  dotted 
lines  show  places  to  bend  vertical  treadle  to  form  horizontal  treadle  c. 


out  through  a  rubber  hose  which  is  pushed  down  the  open  hole  and 
then  tightly  surrounded  by  dirt.  Contrivances  of  this  sort,  such  as 
the  Eureka  Squirrel  Exterminator,  are  on  the  market.  Then  there  are 
gopher  "bombs"  which,  when  lighted  and  placed  in  the  burrows  and 
covered,  are  supposed  to  generate  a  poisonous  gas  that  will  kill  the 
gopher.  As  with  carbon  bisulphide,  the  gas  often  fails  to  reach  the 
gopher  because  of  obstruction  and  elevations  in  the  winding  burrows. 
Experiments  have  shown  that  with  gasoline  at  20  cents  and  carbon 
bisulphide  at  90  cents  a  gallon,  the  bisulphide  was  more  effective  and 
cheaper  than  gasoline. 


5.  ENCOURAGEMENT  OF  THE  GOPHER'S  NATURAL  ENEMIES 

Comparatively  few  ranchers  realize  the  full  value  of  barn  owls  and 
gopher  snakes  as  allies  in  their  war  on  gophers.  A  pair  of  nesting 
barn  owls  was  found  by  the  writer  to  catch  from  three  to  six  gophers 
a  day  for  their  young.  No  one  who  has  ever  counted  the  number  of 
rodents  brought  in  by  a  pair  of  these  owls  during  a  single  season  would 
ever  doubt  their  value  as  gopher  destroyers. 

On  May  13,  1914,  near  Mendota,  Fresno  County,  Mr.  John  G. 


348  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Tyler*  found  two  pairs  of  barn  owls  nesting  in  an  old  tank  house. 
' '  One  nest  was  placed  in  the  tank  on  the  bones,  fur,  pellets,  and  refuse 
that  had  accumulated  to  a  depth  of  several  inches.  One  bird  was 
perched  on  a  beam  overhead  asleep,  while  his  mate  occupied  the  nest, 
which  contained  four  very  small  birds  and  six  eggs.  Scattered  about 
on  the  floor  were  five  pocket  gophers  (Thomomys) ,  five  kangaroo  rats 
(Perodipus) ,  one  pocket  mouse  (Perognathus),  and  two  white-footed 
mice  (Peromyscus),  all  of  which  were  in  good  condition  and  un- 
doubtedly of  the  previous  night's  capture.  Besides  these,  there  were 
partly  eaten  remains  and  fresh  skeletons  of  several  more.  ...  If  the 
thoughtless  persons  who  so  relentlessly  destroy  this  owl  on  account 
of  its  supposed  fondness  for  chickens  and  pigeons  would  take  the 
trouble  to  keep  watch  of  a  nest-site  through  one  season,  the  most 
ignorant  among  them  could  hardly  fail  to  realize  that  they  are  working 
against  their  own  best  interests  whenever  they  kill  a  barn  owl. ' : 

The  gopher  or  bull  snake  may  steal  eggs  occasionally,  but  his  main 
diet  consists  of  small  rodents,  chiefly  gophers.  A  wise  man  will  there- 
fore protect  the  gopher  snakes  on  his  premises.  Every  gopher  that 
the  barn  owl  or  gopher  snake  destroys  means  one  less  for  you  to  catch. 

OTHER  METHODS  OF  CONTROL 

Some  other  methods  of  controlling  pocket  gophers  are:  (a)  pro- 
tecting trees  with  wire  netting ;  ( b )  planting  gopher-repellent  plants ; 
(c)  using  rodent  virus;  (d)  surrounding  small  plots  by  a  trench;  (e) 
protection  of  ditches  by  cement. 

(a)  Protecting  Trees  with  Wire  Netting 

One-inch  mesh  galvanized  wire  netting  in  the  form  of  a  cylinder 
one  foot  in  diameter  and  eighteen  inches  high  may  be  placed  about 
young  trees  when  they  are  planted,  to  protect  them  from  the  attacks 
of  gophers.  The  top  of  the  netting  should  be  put  just  below  the  surface 
of  the  ground,  and  the  trunk  of  the  tree  above  ground  protected  in  some 
other  way  so  as  not  to  interfere  with  shallow  cultivation,  which  the 
net  ling  will  certainly  do  if  it  sticks  above  ground. 

(b),  (c)   Gopher-Repellent  Plants;  Rodent  Virus 

Plants  which  will  drive  gophers  away,  and  a  virus  of  a  "gopher 
infectious"  disease,  have  both  been  much  exploited,  but  neither  remedy 
Seems  to  have  "made  good"  and  neither  can  be  recommended. 

Condor,  XVI F,  .January,  1915,  p.  57. 


Bulletin   340]  CONTROL  OF   THE  POCKET   GOPHER  349 

(d)  Surrounding  Small  Plots  by  a  Trench 

Small  plots  of  ground  have  been  protected  by  being  entirely  sur- 
rounded by  a  trench  eighteen  inches  wide  and  two  feet  deep,  with 
open  five-gallon  cans  buried  flush  with  the  bottom  in  the  ditch  at 
twenty-five  foot  intervals,  to  catch  and  hold  the  gophers  which  tumble 
into  the  ditch,  and  thence  into  the  cans. 

(e)  Protection  of  Ditches  by  Cement 

A  power  company  which  had  much  trouble  with  gophers  in  a  large 
ditch  dug  a  four-inch  trench  six  feet  deep  straight  down  through  the 
middle  of  the  lower  bank  of  the  ditch.  The  dirt  was  loosened  with  an 
iron  bar  and  removed  with  a  narrow  shovel  of  the  type  used  in  digging 
telephone-pole  holes.  The  trench  was  then  filled  with  a  "lean"  mix- 
ture of  cement  and  sand,  which  was  carried  on  a  barge  that  floated 
on  the  water  in  the  ditch.  The  cement  was  conveyed  to  the  bottom  of 
the  trench  by  a  galvanized  iron  chute  which  was  built  in  sections  so  as 
to  be  readily  adapted  to  any  depth.  This  method  was  said  to  have 
been  expensive,  but  satisfactory  in  the  long  run. 

A  small  irrigation  ditch  having  a  seven-foot  "surface"  has  been 
protected  from  gophers,  weeds  and  leakage  by  applying  to  the  sides 
and  bottom,  first  a  %-inch  coat  of  1  to  7  cement  and  then  a  surface 
layer  i/^-inch  thick  of  1  to  3  cement.  This  treatment  proved  satis- 
factory. 

All  of  these  preventives  are  costly  and  are  advisable  only  in  those 
situations  where  protection  against  gophers  cannot  be  obtained  by 
their  destruction. 

Transmitted  October  31,  1921. 


350 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  5. — Diagram    showing   methods   of   destroying   gophers   to   be   used   at 
various  seasons  of  the  year. 


